The present invention relates to a multichamber or multilevel press especially for the hot pressing of plate-shaped or board-shaped workpieces of wood or woody materials which may be covered with films impregnated with or coated by glue, veneers or the like. More particularly this invention relates to a multichamber or multilevel press having a fixed press plate between upper and lower movable platens defining chambers receiving the flat workpiece to be pressed with the press plate and between each other.
German Patent Document DE-U 88 06 883 describes a press with two chambers multichamber or multilevel press which comprises a press frame, a press plate or table fixed in this frame, vertically movable press platens above and below the press table and piston-and-cylinder units for displacing the movable press platens.
European Patent Document EP-B 0 384 958 and German Patent Document DE A 4428 786 describe multichamber presses with a number of movable press platens and piston-and-cylinder units whereby the piston-and-cylinder units connect two movable press platens. The piston-and-cylinder units chain the movable press platens together. In accordance with this principle, more than two press chambers can be provided one above another. However, the vertical guidance of the press platens is unsatisfactory in these systems. In EP-B 0 384 958 and DE A 4428 786 there is always the danger that a movable press platen will tilt upon pressing.
It is, therefore, the principal object of the present invention to provide a high capacity multichamber press whereby the danger of platen tilting is eliminated at a modest cost.
More specifically, it is an object of this invention to provide a multichamber or multilevel press, especially for press wood or woody materials with laminates like foils or films coated with glue, or with veneers, whereby drawbacks of earlier systems are avoided.
These objects and others which will become more readily apparent hereinafter are attained, in accordance with the invention in a multichamber or multilevel press which comprises:
a press frame having a plurality of uprights;
a press plate fixedly mounted in the frame and secured to the uprights;
a plurality of vertically movable press platens received in the frame and including movable press platens above and below the press plate and defining pressing chambers with the press plate;
respective first groups of mutually parallel jointly operable piston-and-cylinder units acting upon the press platens for displacing the press platens toward and away from the press plate and including piston-and-cylinder units braced between the frame and respective ones of the movable press platens proximal to the press plate, the movable press platens including at least one further movable press platen forming a group with a the movable press platen proximal to the press plate and defining at least one further pressing chamber therewith;
at least one second group of mutually parallel jointly operable piston-and-cylinder units braced between the further movable press platen and the press platen defining the further chamber therewith for expanding and contracting the further chamber;
a respective mechanical synchronizing device on each of the movable press platens most distal from the press plate for vertically guiding the movable press platens, the mechanical synchronizing devices including:
a plurality of gears spaced from one another on outer sides of the respective movable press platen,
shafts rigidly interconnecting the gears, and
racks on the uprights meshing with the gears; and
control means coupled with the groups of piston-and-cylinder units for selectively and alternatingly opening and closing the chambers.
With the system of the invention, above and/or below the fixed press table or press plate, a press platen arrangement is provided which has at least two movable press platens disposed one above the other at movable press platens being interconnected by a group of piston-and-cylinder units operated in parallel and the press platen of the group of press platens which is most distal from the stationary press plate is provided with a mechanical synchronizing unit for vertical guidance of the movable press platens.
According to the invention, the synchronizing device comprises gears or pinions which are spaced apart on the outer sides of the outer most movable press platens, namely, the press platens most distal from the stationary press plate and these pinions are rigidly interconnected by respective shafts and roll on and mesh with respective racks on the uprights of the press frame. The apparatus also includes means for alternatingly and selectively opening and closing the press chambers formed by the movable platens. The movable press platens on each side of the stationary press plate are chained together by respective groups of piston-and-cylinder units.
Each thus coupled group of press platens is connected by the first group of piston-and-cylinder units to a rigid part of the press, namely, to the frame which in turn is rigidly connected to the press table or press plate.
Surprisingly, it has been found that the synchronizing device need only be provided on the movable press platen most distal from the press plate among the press platens of the group on the respective side of the press plate and suffices to guide all of the movable press platens on that side of the press plates when the press chambers are alternatingly opened and closed.
If a press chamber between movable press platens is closed, with a workpiece in that chamber to be pressed by the press platens, that assembly of closed press platens and workpiece forms a guide which maintains parallelism with any movable press platens connected thereto and thus the synchronizing device on that unit functions to maintain synchronized closing of all other chambers on that side of the press plate. Parallelity is thus maintained between all of the press platens on the respective side of the press plate in spite of the fact that only a single synchronizing unit is provided on each side.
The mechanical synchronizing unit is so dimensioned that any nonuniform pressure distribution developed in the pressing operation can be compensated by a mechanical redistribution. It has been found to be advantageous to connect the gears at the outer edges of the respective movable press platen by two parallel rigid shafts and to couple the two parallel shafts with each other by bevel gearing and a coupling shaft.
While there is the danger of overloading if a foreign body is found in the press chamber during the press operation, according to the invention an emergency switching can be effective by providing the bearing housing for one of these shafts if a two part housing with one part connected to the movable platen and the other part braced thereagainst under spring loading. The movable part of the bearing housing can be connected with a switch which can issue a stop command in the case of such an overload. If there is a tendency of one of the movable press platens to tilt, therefore, the movable bearing housing half will trigger the switch and produce the stop signal.
The synchronizing devices have further guide rollers which are at a right angle to the respective gear wheels or pinions and ride upon something or planar tracks on the uprights or columns. The columns may be spaced apart along the longitudinal sides of the press plate and connected therewith by bolting or welding and the first group of piston-and-cylinder units can be braced against these columns.